Product overview Sensors - BURKERT FLUID CONTROL SYSTEMS - #9

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table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:4.00pt "Arial", sans-serif; } .font1 { font:6.00pt "Arial", sans-serif; } .font2 { font:7.00pt "Arial", sans-serif; } .font3 { font:8.00pt "Arial", sans-serif; } .font4 { font:17.00pt "Arial", sans-serif; } .font5 { font:20.00pt "Arial", sans-serif; } 16 Burkert | Sensors, Transmitters and Controllers Flow, Batch and Ratio Measuring Principles - Non Moving Parts Magnetic inductive flow meters Magnetic inductive flow meters, also known as magmeters, obtain the flow velocity by measuring the changes of induced voltage of the conductive fluid passing across a controlled magnetic field. Magmeters may be designed as full bore magme-ters or insertion magmeters. Ultrasonic flow meter A pair of transducers each working as a receiver or trans-mitter, are placed in the wall pipe with a specific distance (L). Both transducers send out an acoustic wave signal at the same time to the downstream and the upstream receiver. The signals are reflected by 2 mirrors; one on the upstream side of the pipe and the other on the downstream side of the pipe. The traveling time of both signals is measured by an integrated electronic board. The time for acoustic waves to travel from the upstream transducer 1 to the downstream transducer 2 is shorter than the time it requires for the same waves to travel from the downstream to the upstream. The difference in traveling time is directly proportional to the flow speed (V). The larger the difference, the higher the flow ve­locity. With this measuring principle it is possible to measure all kinds of water based fluids with a turn down ratio of up to 1:250. Conductive as well as non conductive fluids can be measured without any problems and having no moving parts means the maintenance costs are negligible. Differential pressure flow meter Differential pressure flow meters employ the Bernoulli equa­tion that describes the relationship between pressure and flow velocity. A flat orifice plate with an opening is inserted into the pipe and placed perpendicular to the flow stream. As the fluid pas­ses through the orifice plate, the restricted cross section area causes an increase in velocity and decrease in pressure. The pressure difference before and after the orifice plate is used to calculate the flow velocity. The larger the pressure difference, the higher the flow velocity. The turn down ratio between smallest and highest measurable flow is about 10:1. Conductive as well as non conductive fluids can be mea­sured without any problems. Having no moving parts, the maintenance costs are negligible. The measurable liquids can vary between clean, dirty and viscous fluids. Depending on the orifice plate size, it may be necessary to filter the fluid. Insertion magmeter An Insertion finger sensor element is mounted on one wall side and is in contact with the fluid. An electric coil which is placed near the top of the finger generates a constant alterna-ting magnetic field B in the flow path. According to Faraday's law of electromagnetic induction, a conductive fluid passing across the magnetic field induces a current flow between the 2 electrodes which can be measured as a voltage. The 2 electrodes are placed at the tip of the flow finger. The higher the flow speed v, the higher the created voltage. Integrated electronics convert the voltage signal into a standard signal (e. g. 4 - 20 mA or pulse). The design of the Insertion magmeter is very compact and can also be easily installed into existing pipe systems. Inser­tion magmeters are suitable for flow measurement of vir-tually all conductive fluid media - even with a high level of contamination. Only non-conductive fluids <20 us, coating type liquids or highly abrasive fluids restrict application options. Due to the fact that only one point of the pipes cross section is used to measure the fluid velocity, the accuracy is slightly less then that of a full bore magmeter. Full bore magmeter Two electrical coils are placed around the pipe of the flow to be measured and sets up a pair of electrodes across the pipe wall. The two coils generates a constant and homoge-neous alternating magnetic field in the flow cross section. According to Faraday's law of electromagnetic induction, a conductive fluid passing across the magnetic field induces a current flow between the 2 electrodes which can be mea­sured as a voltage. The higher the flow speed v, the higher the created voltage. Integrated electronics converts the volt­age signal into a standard signal (e. g., 4 - 20 mA or pulse). For the full bore magmeter, the induced voltage is detected by electrodes, which are arranged directly opposite of each other measuring the induced voltage of the entire pipe cross section. The advantage is that the entire flow profile can be detected. This results in very precise measurement of the medium velocity. Only non-conductive fluids <5 us, fluids causing coatings or highly abrasive fluids restrict application options. Upstream pressure Downstream pressure Il ' 2 Induced voltage Induction coil Electrodes Magnetic field Fluid velocity Orifice plate